Societies around the world are much inflicted by cardiovascular diseases. Cardiovascular diseases are still among the leading causes of deaths worldwide. Lack of exercise, unhealthy diet and other factors may lead for instance to stenoses, a condition where part of the cardio vasculature is constricted. The strictures may cause undersupply of tissue downstream the stenosis. Although treatments of stenoses are available, these are largely interventional and are not without risks. For instance, one interventional procedure is the introduction of a stent into the vasculature via a catheter. The stent is then navigated to the stenosed site and made to expand there in order to enlarge and so restore lost vessel cross-section. But these types of interventional treatments are not without risk and they put strain on already cash-strapped national health services—sometimes even unnecessarily. For instance, if a stricture occurs in a part of vessel that supplies already moribund tissue, it is questionable whether the intervention will actually result in any positive health effects. The moribund tissue cannot be revived and the blood flow, limited as it may be because of the stricture, may still be just enough in some cases. The technique of FFR (fractional flow reserve) determination comes to the aid here as it allows assessing the severity of the stenosis in terms of a score, that is, a number. FFR is a measure of stenosis' severity besides coronary artery geometry, because it includes the impact of the stenosis on blood flow. The clinical relevance of invasive FFR measurements during catheterization procedures has been proven in clinical studies. Medical staff can then better judge whether an intervention is warranted in the circumstances. One way to establish this number is to take in-situ measurements that include differential pressure across the stenosed site and blood flow rate therethrough. A special catheter is used for this that is equipped with suitable probes to take the measurements. The catheter is placed distal and then proximal to the stenosed site to establish in particular the pressure differential. But again, this is not without risk either as the catheter will need to be forced through the stenosed site. Also, the interventional tool itself is complex and expensive to procure and there usually is the need to administer potentially harmful substances such as Adenosine to increase hyperemia in the cardio region.
Therefore non-invasive local FFR estimation methods for catheterization lab application have been proposed in the past to avoid the use of expensive in-situ pressure measurement equipment. A variant of these methods is based on volumetric data reconstructed from CT projections. Another variant of this method is in general based on volumetric models of the coronary arteries generated from a set of angiographic projections (3D coronary angiography (3DCA)). Both variants are based on computational fluid dynamics (CFD) simulations.
These known methods were observed to be at times computationally expensive and/or tend to incur relatively high dosage for the patient.